Hard water looks like nothing at all in a glass, which is why people ask. What it looks like is everything it leaves behind, and those marks are distinctive enough that a walk around the house identifies it in a couple of minutes without any test. One common appearance is regularly mistaken for hardness and is something else entirely.
The white deposits
Chalky white crust on the kettle element, around tap spouts, on the shower head where jets block or spray unevenly, and along the edges of shower screens. That deposit is the dissolved calcium and magnesium left behind as water evaporates or is heated, and it is the clearest visual sign there is. It comes back after cleaning, which is the giveaway: dirt cleaned away stays away, while scale returns on a schedule set by how hard the water is.
Films, spots and dull surfaces
Glassware coming out of the dishwasher with a cloudy film or white spots. A haze on shower screens that returns within days of cleaning. Dull, stiff laundry that has changed gradually over a year rather than suddenly. Soap scum lining the bath, which is hardness reacting with soap to form an insoluble residue rather than dirt. Each of these is the same chemistry appearing on a different surface, and together they are more convincing than any one of them alone.
What is mistaken for it
Cloudy water that clears from the bottom upwards within a minute is dissolved air, not hardness, and it is common on cold mains water and after work on the pipes. Orange or brown staining is iron. Black or dark staining is manganese. Blue green staining is dissolved copper from acidic water attacking the plumbing. None of those is hardness and none is fixed by a softener, which is worth knowing before buying one to deal with a colour problem.
Turning the look into a number
The USGS classifies hardness as dissolved calcium and magnesium, with soft at 0 to 60 mg/L as calcium carbonate, moderately hard at 61 to 120, hard at 121 to 180 and very hard above 180, and much of the trade reports the same thing in grains per gallon, whose figures are far smaller. On a community supply the utility publishes the figure at no cost; on a well a test kit gives it. Our softener cost guide covers what treatment costs once you have the number.
Questions people ask about what does hard water look like
Does hard water look cloudy?
No. It is clear in the glass. Cloudiness that clears from the bottom upwards is dissolved air, which is unrelated to hardness.
What is the clearest visual sign?
White chalky deposits on the kettle element, tap spouts and shower head that return after every cleaning.
Is orange staining hard water?
No, that is iron. Black staining is manganese and blue green is copper from acidic water. None are fixed by a softener.
How do I get an actual figure?
From the utility's annual report on a community supply, at no cost, or from a hardness test kit on a private well.